Embodiments of the present invention relate generally to semiconductor devices. More particularly, some embodiments of the invention relate to a power semiconductor rectifier device and a method of making the device.
Power semiconductor rectifiers are used extensively in power supplies and power converters. In order to provide a DC voltage, diode rectification has been used for many years in switching mode power supplies. However, the scaling down of semiconductor technology calls for lower voltage and larger current power supply. A PN diode is typically can have a forward voltage drop of around 0.6-0.8V. For 3V output application, this limits the theoretical efficiency of a DC/DC power converter. For a 2V application, the efficiency is even lower and becomes unacceptable. Because the diode forward drop voltage cannot be scaled down further, diode rectification can no long meet the smallness, thinness, and high-efficiency requirements desired by the consumer. Furthermore, since circuit loss is proportional to output current, diode rectification suffers from excessive loss with large output current.
As an alternative, a Schottky diode can provide a lower voltage drop, from 0.2-0.4 volts, for example. However, fabricating Schottky diodes is a more complex process and tends to increase the cost of the device. Thus, even though widely used, conventional rectifiers, such as PN diodes or Schottky diodes, suffer from many limitations. Theses limitations include high cost and complex circuit. More details of these and other limitations are described below.
Therefore, devices and methods for improved semiconductor rectifying devices are highly desirable.